Oozing with Life, and Maybe Iron

The Palmer has an ample supply of Dutch hot chocolate mix to warm people as they come in from the wind, spray, and snow on deck. Today I fixed my cup as normal, but I walked away from the galley without a spoon.

As I sloshed and swirled my cup, hoping the hot chocolate powder would mix with the hot water, I realized I was facing the same problem that phytoplankton face in the Ross Sea. At the bottom of my cup were a whole bunch of particles that I wanted, while at the top there was only clear water.

If I could get just some of the powder up to the top, the water would be sweet and chocolatey, and I’d be happy. But even though I was adding a considerable amount of energy in the form of swirling, I still had to go back and get a spoon. If all that work couldn’t mix the chocolate just a few inches in my cup, how does mixing happen at sea, where nutrients have to move up through thousands of feet of water?

This is one question that Dr. Phoebe Lam has spent much of this voyage thinking about—and it has prompted her to start looking at what lies on the bottom of the Ross Sea in more detail. We’ve been looking over her shoulder. Read on through the slideshow to see what she has found:

For the rest of our expedition, the Palmer is going to crisscross two shallow parts of the Ross Sea: Mawson Bank and Pennell Bank. Dr. Lam will be sampling the seafloor as we cross, and Dr. Kohut’s and Bruce Huber’s teams will measure the currents that flow along the seafloor. Here’s a map of the area to help you keep straight the parts of the Ross Sea we’re studying:

If the Ross Sea is getting mixed like a giant cup of hot chocolate, how is it happening? Dr. Lam’s analyses will tell us about the particles on the seafloor: how much iron is there, and whether particles of it might be reaching the phytoplankton.

To move that iron up to the surface waters will take a lot of energy. Dr. Kohut’s and Bruce’s measurements will help decide if the bottom currents are providing enough. And the terrain of the seafloor, as shown on the map, might be acting like that spoon I needed today—a hard surface that deflects the swirling currents upwards. That’s why the scientists are focusing on these two shallow banks and their sloping sides.

Many thanks to Dr. Angelicque White and Dr. Scott Fay for help with the seafloor creatures, and to Kathleen Gavahan for plotting the map.

About Hugh Powell

Hugh is a staff writer at the Cornell Lab of Ornithology and is on special assignment with the Rutgers University Institute of Marine and Coastal Sciences. He has previously written for the Woods Hole Oceanographic Institution.